Build a business case that survives the journey

A business case is, of course, a financial exercise that quantifies the business benefits an organisation should expect to receive from a project. But it is also a vital tool for aligning different stakeholder interests with an organisation and keeping the organisation bought into the project throughout its lifetime and afterwards.

The point about alignment is often overlooked or underappreciated. Core transformations are complex and expensive projects. If an organisation does not articulate clearly enough, widely enough or often enough what it seeks to achieve with the project, the project will always be at risk of being stopped. Furthermore, the articulation of purpose should capture the goals of all the teams involved and consistently report on them.

When it comes to building the financial case, the exercise is not finished when the model is built. It is essential to track the financial case, to show that benefits are being realised during the project, and, once fully operational, to track expectations against reality and understand where the variances arose – to try to mitigate negative variances and double down on the positive variances. As we’ll discuss in Part 2 of this playbook focused on migration, there are various factors, such as training, that tend to account for significant variation.

But the financial case is not enough. A business case should be constructed across four economic dimensions: operational, commercial, structural and strategic. And in each dimension, opportunity cost should be considered. As we said in the introduction to this playbook, 2026 is the year when the cost of not changing will exceed the cost of changing, and much of that cost is opportunity – the benefits foregone.

Run the institution simpler

Modernisation must first demonstrate operational credibility. Infrastructure rationalisation and reduced maintenance spend provide early proof. But the deeper gain lies in simplifying the operating model.

A structurally modern core removes manual reconciliations, reduces regression overhead and eliminates the silent tax of technical debt. Over time, capacity shifts from control-heavy back-office functions toward customer-facing and revenue-generating activity.

Cost efficiency is not about running cheaper systems. It is about running a structurally simpler institution. The opportunity cost is money sunk into running the institution rather than introducing genuine innovation that moves the needle on customer experience. But it is wider: consider, for instance, the drag on talent acquisition that comes from hiring people to do data reconciliation rather than on activities that create lasting value.

Grow faster

Speed-to-market is not just an operational metric; it is a revenue multiplier.

In business model terms, this is likely to manifest across a range of metrics, from lower customer acquisition costs to higher revenues per customer and per employee, as cross-sell opportunities arise.

There is also the possibility of adapting distribution and sourcing models with a 4th-generation core. Put simply, an institution can tap into third-party distribution channels through embedded finance, lowering the cost of customer acquisition and driving volume to improve unit economics. It can also source products and services from third-party providers, leveraging its distribution power to increase revenue per client.

In terms of the opportunity cost, institutions must try to estimate the cost of deferring action, both in terms of revenue foregone and the leaking of customer goodwill to faster-moving and more dynamic competition.

Protect the institution

Modernisation reshapes institutional risk. A well-architected 4th-generation core materially reduces several categories of risk. Operational risk declines as manual dependencies are removed. Technology risk declines when unsupported legacy platforms are retired. Compliance improves when controls operate on real-time data rather than retrospective reports. Cyber risk reduces as outdated infrastructure is retired, encryption standards improve and security architectures evolve toward zero-trust principles.

But acceleration introduces new dynamics. Transaction velocity increases exposure speed. Ecosystem participation expands dependency chains. Continuous deployment increases change frequency.

The business model must then attempt to weigh up the benefits of risks mitigated but also plan for new risks. The outcome will be overwhelmingly positive, especially when the opportunity costs of operational failure, customer trust erosion and systemic decline are factored in, but the cost of new risk systems must not be overlooked.

Preserve strategic freedom

Strategic optionality is rarely modelled, but it is where the greatest long-term value resides. A structurally modern core enables business model agility, ecosystem participation without architectural lock-in and the ability to absorb acquisitions without systemic shock. Importantly, it also reduces the likelihood of another forced re-platforming cycle.

Optionality is not abstract. It is the economic value of not being trapped. It is clear that the pace of change is accelerating, making it increasingly difficult to predict what the future holds. Therefore, the opportunity cost of not having technology that will allow an institution to change as it needs, to capitalise on new technologies such as GenAI, or to adapt to new regulations, market changes, or competitive threats is one that no boardroom should accept.